Numerous vehicles of the track or wheel type to perform various material handling operations have been proposed. One type of vehicle that has received a considerable degree of attention is a small unit that incorporates four wheels which are driven by two separate power sources and the steering or turning movement is accomplished by driving the pair of wheels on one side of the vehicle in one direction while the second pair of wheels is either in a neutral condition or driven in the opposite direction. These vehicles have generally been referred to as skid steer vehicles.
One type of skid steer vehicle that is presently commercially available incorporates hydraulically actuated fluid translating devices as the power train between the engine and the respective pair of wheels. In order to simplify the construction and reduce the cost of vehicles of this type, the actuation of the fluid translating devices is controlled through manual control levers that respectively cooperate with the two translating devices on opposite sides of the vehicle and the fluid translating devices are maintained in engagement by manual forces applied to the control levers. The control levers may additionally function to control the movement of the lift arms and the material handling attachment. For safety reasons, the control systems are designed to automatically return to a neutral position upon release of the control levers.